Preheat the oven to 400°F and lightly spray a 9x13-inch baking dish with nonstick cooking spray. Brown sausage and onion till done and drain.
Combine sausage and cheese and put in the prepared baking dish.
Mix Bisquick, milk, eggs, and a dash each of salt and pepper. You can also add your favorite seasoning here. I love to add a little Jane’s Krazy Mixed Up Salt to eggs. Pour over sausage.
Sprinkle cheese over top.
Bake for 25 minutes or until eggs are set.